grid interconnection of embedded generators not for bidding

7/23/2019 Grid Interconnection of Embedded Generators Not for Bidding

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CEB Guide for Grid Interconnection of Embedded Generators, Sri Lanka December 2000Part 2: Protection and Operation of Grid Interconnection

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CONTENTS OF PART 1 OF THE GUIDE (SEPARATELY BOUND)

Information Cop" # $ot for BiddinCEB Guide for Grid Interconnection of Embedded Generators, Sri Lanka December 2000Part 2: Protection and Operation of Grid Interconnection

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CONTENTS OF PART 2 OF THE GUIDE

Glossary, De!"!#!o"s a"$ A%%re&!a#!o"s '1 S#$!es a"$ I"or*a#!o" #o %e E+-a".e$ 11!&! Stabi'it" !!!&2 (au't Le)e' !2

!&% Protection !2!&* +o'tae Le)e's !%!&*&! Interconnection +o'tae !%!&*&2 +o'tae ('icker !%!&*&% +o'tae ise !*!&*&* Studies on +o'tae ('icker and +o'tae ise !*!&- Eart.in !*!&/ Load ('o !*2 Fal# Le&el 1/2&! Genera' !-2&2 (au't Le)e' Information !-2&% (au't Le)e' Ca'cu'ation !-2&* (au't Le)e' eduction and 1itiation !0 ol#a.e Re.la#!o" 1%&! Genera' !3%&2 +o'tae Limits !3%&% Poer (actor e4uirements !53 Ear#-!". o Ele#r!!#y Ne#4or5s a"$ E*%e$$e$ Ge"era#ors 26*&! Genera' 20*&2 CEB E'ectricit" Supp'" $etorks 20*&% Compatibi'it" of $etork and Generator Eart.in 2!*&* Generator Para''e' Eart.in 2!*&- Interconnection of CEB and Generator Eart. S"stems 2%*&/ Desin of Eart. S"stems 2-/ Sy"-ro"!sa#!o" o Ge"era#ors 2'-&! Genera' 2/-&2 +o'tae ('uctuation 2/

-&% S"nc.ronous Generators 2/-&* 6s"nc.onous Generators 2/-&- Ot.er 7"pes of Generators 2-&/ S"nc.ronisin C.eck re'a" 2' Isla"$e$ O7era#!o" 2/&! Genera' 23/&2 8a9ards of Is'andin 25/&2&! neart.ed Operation of t.e Distribution S"stem 25/&2&2 Loer (au't Le)e's %0/&2&% Out of s"nc.ronisation rec'osure %0/&2&* +o'tae Le)e's %0/&2&- ;ua'it" of Supp'" %!/&2&/ isk to 1aintenance Personne' %!/&% Common Cause 7rippin %!




Pae */&%&! Genera' %!

/&%&2 isks to t.e $etork %!/&%&% isks to t.e Generator %2/&* Sources of Common Cause 7rippin of Generators %2/&*&! Loss of 1ains e'a"s %2/&*&2 +o'tae e'a"s %2/&*&% (re4uenc" e'a"s %%/&*&* Loca' Generator Instabi'it" %%8 Isla"$!". De#e#!o" a"$ Pro#e#!o" 03&! Genera' %*&2 Is'andin Detection S"stems and Settins %-&2&! Genera' %-&2&2 O)er and nder +o'tae %-&2&% O)er and nder (re4uenc" %-&2&* ate of C.ane of (re4uenc" %/&2&- +o'tae +ector S.ift %/&2&/ e)erse +6s %3&2& Intertrippin %3&2&3 (au't 7.roer %5&2&5 estoration %5&2&!0 (uture De)e'opments %5&% Is'andin $etork Protection *0&%&! Genera' *0&%&2 In.ibitin of ec'ose De)ices *0&%&% $eutra' +o'tae Disp'acement <$+D= Protection *! I*7le*e"#a#!o" o Isla"$!". Pro#e#!o" 303&! Genera' *%3&2 Interconnection Protection e4uirements *%

3&2&! Case ! *-3&2&2 Case 2 *3&2&% Case % *53&2&* Case * -!3&2&- Case - -%3&2&/ Se'f Commutated Static In)erters -*9 Sr.e Pro#e#!o" //5&! Genera' --5&2 Location of t.e 6rrester --5&% Eart.in -/5&* Se'ection of t.e Li.tnin 6rrestor -/5&- Generators Direct'" Connected to L+ O)er.ead Lines -/16 Har*o"!s /11 O7era#!o"al Proe$res a"$ Re:!re*e"#s /9

!!&! 1eans of Iso'ation -5!!&2 Eart.in (aci'ities for 1aintenance -512 Sae#y As7e#s '6


Pae -A""e+ 1 E+7la"a#ory No#es o" Ear#-!".A""e+ 2 E+7la"a#ory No#es o" Isla"$!". De#e#!o" a"$ Pro#e#!o"A""e+ 0 E+7la"a#ory No#es o" Ne#ral ol#a.e D!s7lae*e"#A""e+ 3 Ty7!al AR *o$elA5"o4le$.e*e"#s

B!%l!o.ra7-y

LIST OF FIGURES IN PART 2



(iure !# Interconnection Protection 6rranement for Case ! */(iure 2# Interconnection Protection 6rranement for Case 2 *3(iure %# Interconnection Protection 6rranement for Case % -!(iure *# Interconnection Protection 6rranement for Case * -%(iure -# 7"pica' Eart.in Options for $etorks it. Embedded Generators 6!:20(iure /# Connection of Eart.in S"stems 6ssociated it. L+>%%k+ Generators 6!:2!(iure # $etork +o'tae Durin an Eart. (au't 6%:-(iure 3# $eutra' +o'tae Disp'acement Protection usin a%#p.ase, -#'imb +o'tae 7ransformer it. an Open De'ta ?indin 6%&/(iure 5# E@amp'e of 7"pica' 6+ 1ode''in Information 6*:2


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PREA;BLE

Embedded Generators .a)e been connected to t.e Ce"'on E'ectricit" Board <CEB=s"stem under Poer Purc.ase 6reements since !55&7.e Poer Purc.ase 6reements beteen Embedded Generators and CEB are

co)ered b" t.e E'ectricit" 6ct of Sri Lanka, and ot.er eu'ations&7.is Guide co)ers t.e re4uirements to be fu'fi''ed b" t.e Interconnection beteen t.eEmbedded Generator and t.e CEB s"stem&7.e Guide is in 7o Parts&Part ! of t.e Guide <separate'" bound= e@p'ains t.e procedure to be fo''oed in makinan app'ication to de)e'op an embedded enerator, e)a'uation b" CEB, and t.eprocess of conductin acceptance tests on t.e Interconnection&Part 2 of t.e Guide e@p'ains t.e studies to be conducted b" CEB to ensure t.einterconnection is safe, and pro)ides uide'ines for effecti)e desin and operation of t.e interconnection&7.is Guide does not rep'ace or supersede an" of t.e re4uirements specified in t.eE'ectricit" 6ct, Ce"'on E'ectricit" Board 6ct, E'ectricit" eu'ations or Poer Purc.ase 6reements&

ASSOCIATED DOCU;ENTS AND PUBLICATIONS

!& Guide'ines on Pri)ate Sector Participation in Sma'' 8"dro Poer De)e'opment,Ce"'on E'ectricit" Board <current issue=&2& Standardised 6reement for Purc.ase of Ener", Ce"'on E'ectricit" Board <currentissue=& AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA 7.is Guide is based on t.e re4uirements of Ce"'on E'ectricit" Board <CEB=, Sri Lanka,and t.e conditions and constraints under .ic. t.e CEB s"stem operates& 7.e primar"intention of t.is Guide is to estab'is. procedures and e4uipment to protect CEBpersonne', e4uipment and t.e s"stem from an" .armfu' effects arisin out of t.einterconnection and operation of Embedded Generators&7.erefore, it s.ou'd not be assumed t.at t.e uide'ines pro)ided ou'd satisf" a'' t.eprotection re4uirements of t.e Embedded Generators& $o responsibi'it" can beaccepted for an" 'oss or damae sustained as a resu't of usin or re'"in on t.is

Guide&


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GLOSSARY, DEFINITIONS AND ABBREIATIONS

AC: 6utomatic +o'tae Contro''er AR< 6utomatic +o'tae eu'ator CEB< Ce"'on E'ectricit" Board, a bod" Corporate du'" constituted b" 6ct $o& !of !5/5 of t.e Democratic, Socia'ist epub'ic of Sri Lanka&Ca7#!&e Ge"era#!o"< Generatin p'ant a)ai'ab'e at CEB customer faci'ities, butnot connected in para''e' it. t.e CEB netork&

Ca7#!&e L!"e Loa$< Load, up to t.e !st point of automatic iso'ation, .ic. is <or ma" be= supp'ied b" an Embedded Generator, e@c'udin Capti)e Loca' Load&Ca7#!&e Loal Loa$< Load it.in t.e Embedded Generator premises inc'udin



enerator au@i'iariesCa7#!&e Loa$< 7.e sum of Capti)e Line Load and Capti)e Loca' LoadCo**o" ;o$e (or Case) Tr!77!".< 6utomatic remo)a' of to or moreeneratin p'ant from t.e s"stem oin to a cause t.at is common to bot. or a''t.e enerators&Co*%!"e$ Hea# a"$ Po4er (CHP)< 6 p'ant t.at enerates e'ectricit" andsupp'ies t.erma' ener", t"pica''" steam, to an industria' or ot.er .eatinre4uirement&EF< Eart. (au't <protection=E*%e$$e$ Ge"era#or< 6 sin'e enerator, or a roup of enerators, connectedto t.e distribution netork of t.e CEB, at )o'taes beteen *00 + and %% k+&E+7or# o Ele#r!al E"er.y< Supp'" of E'ectrica' Ener" b" a Generator to t.eCEB s"stem&Ge"era#!". Co*7a"y< 6 compan", roup or indi)idua' .o p'an to connect or .as a'read" connected an Embedded Generator to t.e CEB distribution netork&


Pae 3Gr!$ I"#ero""e#!o"< 6 'ink beteen CEB E'ectricit" s"stem and EmbeddedGenerators E'ectricit" S"stem, made for t.e purpose of E@portin or ImportinE'ectrica' Ener"&Gr!$ S%s#a#!o"< 6 CEB substation .ere e'ectrica' ener" at 220 k+ or !%2 k+is transformed into %% k+&H!.-es# (Lo4es#) ol#a.e o a Sys#e*< 7.e .i.est <'oest= )a'ue of operatin)o'tae .ic. occurs under norma' operatin conditions at an" time and at an"point in t.e s"stem&H< 8i. )o'tae, e@ceedin !000 + beteen conductors and /00 + beteenconductors and eart.&I*7or# o Ele#r!al E"er.y< eceipt of E'ectrica' Ener" b" t.e EmbeddedGenerator from t.e CEB s"stem&I"#ero""e#!o" Cer#!!a#e< 6 Certificate issued b" CEB to an Embedded

Generator, after testin t.e interconnection&I"#ero""e#!o" ol#a.e< 7.e nomina' )o'tae at .ic. t.e rid interconnectionis made&I"!#!al A77l!a#!o"< 7.e first app'ication b" an indi)idua' or Compan" aspirin tode)e'op an Embedded Generator&Isla"$!".< 7.e process .ereb" a poer s"stem is separated into to or moreparts, it. enerators supp'"in 'oads connected to some of t.e separateds"stems&Isla"$e$ O7era#!o": 7.e situation t.at arises .en a part of t.e e'ectrica's"stem is disconnected from t.e main rid and is enerised b" one or moreenerators connected to it&Le##er o I"#e"# (LOI)< Issued b" CEB to a Generatin Compan" to sinif"CEBs intent to purc.ase poer from a Generatin Compan" at a particu'ar 'ocation&

LO;< Loss of mains <protection=L< Lo )o'tae, not e@ceedin !000 + beteen conductors and /00 + beteenconductors and eart.&


Pae 5Ne#ral Po!"# D!s7lae*e"# ol#a.e< 7.e )o'tae beteen t.e rea' or )irtua'neutra' point and t.e eart.&ND< $eutra' +o'tae Disp'acement& 6 tec.ni4ue to measure t.e disp'acementof t.e neutra' )o'tae it. respect to eart.&No*!"al ol#a.e< 6 suitab'e appro@imate )a'ue of )o'tae used to desinate or

identif" a S"stem&OC< O)er#current <protection=



OF< O)er#fre4uenc" <protection=O7era#!". ol#a.e< 7.e )a'ue of t.e )o'tae under norma' conditions at a i)eninstant and at a i)en point in t.e s"stem&O< O)er#)o'tae <protection=Po!"# o Co**o" Co7l!". (PCC)< 7.e 'ocation of t.e connection beteen t.eCEB netork and t.e Embedded Generator, be"ond .ic. ot.er customer 'oadsma" be connected on t.e CEB side& 7.e PCC ma" be separate from t.e Point of Supp'" .ere a 'ine is dedicated to t.e connection of an Embedded Generator&Po!"# o S77ly (POS)< 7.e 'ocation of t.e connection beteen t.e CEBnetork and t.e Embedded Generator&Po4er Pr-ase A.ree*e"# (PPA)< 6n areement beteen t.e CEB and t.eGeneratin Compan" for t.e purc.ase of e'ectricit" b" t.e CEB&ROCOF< ate#of#c.ane of (re4uenc" <protection=RP< e)erse Poer <protection=SBEF: Standb" Eart. (au't <protection=S7!""!". Reser&e< 7.e difference beteen t.e tota' a)ai'ab'e capacit" of a''eneratin sets a'read" coup'ed to t.e s"stem and t.eir tota' actua' 'oadin&S#e7 ol#a.e< 7.e difference in surface potentia' e@perienced b" a personbridin a distance of ! m it. .is feet it.out contactin an" ot.er roundedstructure&


Pae !0To- ol#a.e< 7.e potentia' difference beteen t.e round potentia' rise<GP= and t.e surface potentia' at t.e point .ere a person is standin .ere att.e same time .a)in .is .ands in contact it. a rounded structure& GPdefined as t.e ma@imum )o'tae t.at a station roundin rid ma" attain re'ati)eto a distant roundin point assumed to be at t.e potentia' of remote eart.& 7.etouc. )o'tae cou'd be from .and to .and a'so&Tra"serre$ ol#a.e< 7.is is a specia' case of t.e touc. )o'tae .ere t.e)o'tae is transferred into or out of t.e station b" a conductor rounded at a

remote point or at t.e station round, respecti)e'"&TNS sys#e* o Ear#-!".: In t.is eart.in s"stem, t.e supp'ier pro)ides separate$eutra' and Protecti)e conductors t.rou.out t.e s"stem& 7.e Protecti)eConductor is connected to t.e neutra' of t.e source& 6'' e@posed conducti)eparts of a consumers insta''ation are connected to t.e Protecti)e Conductor pro)ided b" t.e supp'ier )ia t.e main eart.in termina' of t.e consumersinsta''ation&TT Sys#e* o Ear#-!".< 6n eart.in s"stem .ere a'' e@posed conducti)e partsof an insta''ation are connected to an eart. e'ectrode pro)ided b" t.e consumer .ic. is e'ectrica''" independent of t.e Source eart.&U< nder#)o'tae <protection=UF< nder#fre4uenc" <protection=ol#a.e Le&el< One of t.e $omina' +o'tae )a'ues used in a i)en s"stem&

S< +ector S.ift <protection= Information Cop" # $ot forBiddinCEB Guide for Grid Interconnection of Embedded Generators, Sri Lanka December 2000Part 2: Protection and Operation of Grid Interconnection

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1 STUDIES AND INFOR;ATION TO BE E=CHANGED

CEB ma" conduct t.e studies 'isted in t.e fo''oin subsections beforeaut.orisin t.e interconnection of an Embedded Generator& 7.ese studies i''be conducted it.in t.e period of )a'idit" of t.e LOI, after t.e GeneratinCompan" pro)ides information s.on in 6nne@ % in Part ! of t.e Guide, and.en t.e CEB is satisfied t.at t.e detai'ed desins for t.e Embedded Generator

are in proress&CEB ma" c.are a fee to conduct t.ese studies and to pro)ide t.e information,



as out'ined in Sub#section -&&! of Part ! of t.e Guide&

11 S#a%!l!#yCEB ma" ana'"se t.e effect of imp'ementin t.e additiona' eneration on t.estabi'it" of t.e CEBs s"stem&Loca' stabi'it" i'' be studied .en t.e additiona' Embedded Generation .as acapacit" reater t.an - 1? or makes t.e tota' eneration capacit" on a sin'e

distribution 'ine reater t.an - 1?&Information re4uired for a stabi'it" stud" s.ou'd be submitted b" t.e GeneratinCompan", irrespecti)e of t.e enerator capacit"&7.is ma" be ai)ed b" t.e CEB for sma'' Embedded Generators, t"pica''" 'esst.an ! 1?& 8oe)er, CEB reser)es t.e ri.t to re4uest t.is information at a'ater date&7.e Generatin Compan" s.a'' pro)ide a mode' of t.e 6utomatic +o'taeeu'ator <6+= of t.e Embedded Generator, .en t.e proposed capacit" iso)er - 1?& 7.e (orm of t.e 6+ 1ode' is s.on in 6nne@ *&7.e Generatin Compan" s.a'' pro)ide a mode' of t.e speed Go)ernor of t.eEmbedded Generator, .en t.e proposed capacit" is o)er - 1?& Importantinformation suc. as t.e inertia constant and o)ernor c.aracteristics s.a'' a'sobe pro)ided&


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12 Fal# Le&el7.e Generatin Compan" s.a'' pro)ide information on t.e t.ree p.ases"mmetrica' sub#transient fau't contribution at t.e Point of Supp'", .en t.e(au't Le)e' Information s.on in 6nne@ % of Part ! of t.e Guide is pro)ided toCEB&7.e cumu'ati)e effect of t.e Embedded Generator s.a'' be assessed b" t.eCEB& 6 stud" i'' be conducted .en t.e cumu'ati)e fau't 'e)e' on a distributions"stem reac.es 50 of t.e ratin of t.e associated distribution sitc.ear&

7.e stud" ma" 'ead to t.e re4uirement for more detai'ed information from t.eGeneratin Compan" for detai'ed ana'"sis&

10 Pro#e#!o" 6 stud" i'' be re4uired to assess t.e effect on t.e distribution s"stem protectionratins and settins if an" of t.e fo''oin situations occur& ?.en t.e ma@imum s.ort circuit current t.at can be produced b" a sin'eEmbedded Generator <meanin a site consistin of one or se)era'eneratin units, interconnected to t.e CEB netork t.rou. a sin'e Pointof Supp'"= is reater t.an 20 of t.e ma@imum s.ort circuit current of t.edistribution s"stem& ?.en t.e cumu'ati)e ma@imum s.ort circuit current t.at can be produced ona distribution 'ine <from a co''ection of eneratin stations= is reater t.an%0 of t.e ma@imum s.ort circuit current of t.e distribution s"stem&

?.en t.ere i'' be net e@port of poer from t.e %% k+ distribution s"steminto t.e !%2 k+ s"stem& 7.is ma" .a)e a particu'ar impact on !%2k+ distanceprotection and a'so on directiona' o)ercurrent protection at t.e ridsubstation&


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13 ol#a.e Le&els131 I"#ero""e#!o" ol#a.e7.e +o'tae at t.e Po!"# o S77ly from t.e Embedded Generator to t.e CEBnetork s.a'' be determined as fo''os:

Embedded Generators it. insta''ed eneratin capacit" up to and inc'udin2-0 k+6, s.a'' be interconnected at t.e L+ distribution )o'tae 'e)e', if t.e



nomina' output )o'tae of t.e enerator is *00 + 'ine to 'ine, %#p.ase or 2%0 +'ine to neutra', %#p.ase&Embedded Generators it. an insta''ed eneratin capacit" e@ceedin!000 k+6 s.a'' be interconnected at t.e .i. )o'tae 'e)e'& 7.e nomina' .i.)o'taes in t.e CEB s"stem are !! k+ and %% k+&(or insta''ed capacit" in t.e rane abo)e 2-0 k+6 to !000 k+6, t.einterconnection )o'tae i'' be determined b" CEB on a case#b"#case basis,dependin on t.e capacit" of t.e transformer substation&7.e Point of Supp'" and its nomina' )o'tae s.a'' be defined b" CEB at t.e timeof issuin t.e LOI& 6fter an" re4uired studies, CEB s.a'' a'so pro)ide t.e app'icab'e norma'operatin )o'tae, ma@imum norma' )o'tae and ma@imum permitted )o'tae att.e POS&CEB s.a'' pro)ide information on t.e poer factor 'imits at t.e POS&If a enerator is direct'" <or c'ose'"= connected to a rid sub#station, CEB s.a''a'so specif" t.e poer factor for t.e enerator&132 ol#a.e Fl!5er 7.e enerator s.ou'd not cause )o'tae f'icker at t.e POS .ic. e@ceeds t.atdefined in CE$LEC Standard BS E$ -0!/0&


Pae !*130 ol#a.e R!se7.e )o'tae rise at t.e POS due to t.e eneration must be it.in operationa''imits&7.e taret bandidt. for )o'tae on t.e %% k+ busbar of a rid sub#station is %&7.e taret )o'tae on t.e %% k+ busbar of t.e rid sub#station is %% k+&133 S#$!es o" ol#a.e Fl!5er a"$ ol#a.e R!se 6 to#stae approac. i'' be re4uired in conductin t.ese studies:Stae I: E@c'ude 'oad connections to distribution 'ines and rid transformersStae II: Inc'ude 'oad connections to distribution 'ines and rid transformers

7.e Stae II stud" i'' be re4uired .en t.e Stae I stud" indicates a potentia'prob'em&

1/ Ear#-!".7.e Generatin Compan" s.a'' pro)ide information about t.e proposed eart.inarranement to t.e CEB& Guidance on eart.in s"stem are i)en in Section *and 6nne@ !&

1' Loa$ Flo4Poer supp'ied b" t.e enerator ma" cause t.erma' o)er'oadin of t.e CEBnetork components, and studies ma" be re4uired on:Distribution lines: consider t.e effects of t.e cumu'ati)e eneration capacit"connected to t.e 'ineGrid sub-station transformer(s): consider t.e effects of t.e cumu'ati)eeneration capacit" connected to t.e sub#station&

132 kV/220 kV lines: consider t.e effects of t.e cumu'ati)e eneration capacit"connected to t.e 'ine from mu'tip'e sub#stations, particu'ar'" t.e effect of a c'osedrin outae&


Pae !-

2 FAULT LEEL

21 Ge"eral(au't 'e)e's in a distribution netork must be maintained it.in desin 'imits&atins of sitc.ear s.a'' be in accordance it. t.e dec'ared desin fau't 'e)e'for t.e maintenance of s"stem protection performance&

7.e connection of a enerator to a distribution s"stem i'' increase t.e fau't 'e)e'on t.e netork .en bot. t.e enerator and rid are connected, and t.e effect



of t.is c.ane s.ou'd be considered&(au't 'e)e's in rura' distribution netorks tend to be re'ati)e'" 'o and t.econtribution of sma''er embedded enerators are not norma''" a prob'em&8oe)er, t.ere ma" be protection prob'ems suc. as under#reac.in of !%2k+distance protection or possib'" on %%k+ o)ercurrent, protection .en t.eEmbedded Generator contribution is inc'uded&

22 Fal# Le&el I"or*a#!o"CEB s.a'' pro)ide t.e desin fau't 'e)e's to t.e Generatin Compan" on fau't'e)e's of t.e s"stem at t.e Point of Supp'"&7.e Generatin Compan" s.a'' pro)ide fau't 'e)e' contribution of enerator<s= att.e Point of Supp'"& 7.e Generatin Compan" s.a'' pro)ide to'erances on t.efau't 'e)e' data pro)ided&7.e information re4uirements are specified in pro#formas s.on in 6nne@ % of Part !&I"$#!o" Ge"era#ors(or induction mac.ines, t.e data set is not standard and, t.erefore, datare4uirements for induction enerators s.ou'd be areed beteen t.e CEB andt.e Generation Compan"&

20 Fal# Le&el Calla#!o"CEB s.a'' be responsib'e for monitorin fau't 'e)e's on t.e distribution netorkand performin detai'ed assessments as appropriate to ensure t.at fau't 'imitsare not e@ceeded&Formatted: Bullets and NumberingFormatted: Bullets and Numbering


Pae !/7.e ca'cu'ation of fau't current 'e)e's s.ou'd inc'ude consideration of t.e mainnetork transformer sources, rotatin p'ant and static con)erter dri)es .ic.ma" transfer ener" into t.e netork&(au't ca'cu'ations s.a'' be based on met.ods defined in t.e IEC 505& 7.e fau't

t"pes are described be'o in order to pro)ide an out'ine, and a commonunderstandin of t.e princip'e 4uantities&;a5e al# le&el7.is is t.e peak as"mmetrica' fau't current after t.e initia' fau't& 7.e fo''oinparameters determine t.is fau't 'e)e': s"stem )o'tae, rotatin mac.ine subtransientreactance and time constant, rid transformer source impedance,netork impedance and o)era'' F> ratio& 7.e ca'cu'ation is based on t.e mostonerous source impedance and netork confiuration to deri)e a ma@imum)a'ue& In netorks it. .i. F> ratio, it is t"pica''" about !&3 @ √2 times t.einitia' s"mmetrica' fau't 'e)e' and is often t.e main 'imitin factor&Brea5 al# le&el7.is is t.e tota' fau't current at t.e instant of circuit breaker fau't interruption& 7.ee'apsed time from initia' fau't is dependent on t.e speed of re'a" and breaker operation, and is t"pica''" in t.e rane of * to 3 c"c'es& 7.e fo''oin parameters

determine t.is fau't 'e)e': s"stem )o'tae, rotatin mac.ine transient reactanceand time constant, rid transformer source impedance and netork impedance&7.e ca'cu'ation is based on t.e most onerous source impedance and netorkconfiuration to deri)e a ma@imum )a'ue& 7.e decrement of enerator fau'tcontribution, particu'ar'" for as"nc.ronous mac.ines, is t"pica''" )er" sinificantdurin t.is period, and s.ou'd be taken into account for detai'ed fau't 'e)e'assessments&S#ea$y>s#a#e al# o"#r!%#!o"7.is is t.e s"mmetrica' fau't current at a time after t.e comp'ete deca" of subtransientand transient fau't contribution from rotatin mac.ines& 7.e stead"statecontribution of s"nc.ronous mac.ines is inf'uenced b" t.e 6+c.aracteristic& 8oe)er, for most purposes, t.is 4uantit" ou'd be used for minimum fau't 'e)e' on'" and, in t.is case, it ou'd be norma' to ne'ect a''

Embedded Generator contribution, and use t.e most onerous source andnetork conditions to deri)e a minimum )a'ue&




Pae !

23 Fal# Le&el Re$#!o" a"$ ;!#!.a#!o"?.ere it .as been identified t.at t.e connection of a ne enerator i'' 'ead toe@cessi)e fau't currents, t.e contribution of t.e enerator can be reduced b" t.euse of additiona' impedance&7.is ma" take t.e form of an iso'atin transformer, a reactor or additiona' 'ent.of circuits& 6n iso'atin transformer is preferred&7.e use of s.ort circuit current 'imiters based on t.e fuse and e@p'osi)e 'inkprincip'e, as a a" of mitiatin t.e effect of increased fau't currents, is notrecommended& 7.is is on t.e rounds t.at t.e" are not fai' safe and t.ere is a'ack of CEB e@perience and information on t.eir re'iabi'it"& 7.is ma" be re)ieedin t.e 'i.t of furt.er de)e'opment and e@perience&esonant 'inks or future 87S, .i. temperature superconductin transformersare a possib'e, but cost'", so'ution&Formatted: Bullets and Numbering


Pae !3

0 OLTAGE REGULATION

01 Ge"eralContro' of )o'tae on t.e distribution s"stem is affected b" t.e connection of embedded eneration& 7.e poer bein fed into t.e rid from t.e embeddedenerator i'' raise t.e )o'tae at t.e POS& 7.is ma" be an acceptab'e supportto 'oca' netork )o'tae or it ma" cause t.e operationa' or statutor" )o'tae 'imitsof t.e 'oca' distribution s"stem to be e@ceeded&7.is )o'tae rise ma" be mitiated b" t.e enerator importin reacti)e poer&

7.e effecti)eness of t.is is dependant upon t.e F> ratio of t.e distributions"stem& (or e@amp'e, a cab'e feeder it. a 'o F> ratio ou'd re4uire a 'areproportion of imported reacti)e poer to .a)e a sinificant mitiatin effect ont.e )o'tae rise at t.e POS&7.e import of reacti)e poer increases t.e current f'o in t.e distributionnetork, 'eadin to additiona' netork 'osses and use of capacit"&7.e consumption of reacti)e poer b" a enerator ma" reduce t.e capacit" andefficienc" of eneratin p'ant due to t.e current 'oadins in t.e enerator stator indins&7.e )o'tae rise at t.e POS ma" a'so be mitiated b" a reduction in t.e upper 'imit of )o'tae at t.e rid substation& 7.is can be ac.ie)ed b" reducin t.ebandidt. and>or t.e taret )o'tae of t.e substation 6+C& 8oe)er, bot.options ou'd re4uire carefu' consideration: educin t.e 6+C bandidt. ou'dpotentia''" increase t.e tap c.ane operation fre4uenc" of t.e rid substation

transformers, reducin t.e taret )o'tae ou'd potentia''" cause remotecustomers to e@perience )o'tae 'e)e's be'o statutor" 'imits& CEB i'' i)ecarefu' consideration to t.e optimisation of netork )o'tae contro', possib'"usin 6+C it. 'ine drop compoundin settins for )o'tae boost and poer factor droop, to encourae t.e connection of embedded eneration it.outcompromisin statutor" ob'iations to e@istin customers&

02 ol#a.e L!*!#s8a)in determined an optimum taret )o'tae and 'imits for )o'tae at t.e ridsubstation, t.ese 'imits s.a'' be dec'ared and be a)ai'ab'e to a'' prospecti)eGeneratin Companies& See section - of Part ! on information to be pro)ided b"t.e CEB&Formatted: Bullets and Numbering

Information Cop" # $ot for BiddinCEB Guide for Grid Interconnection of Embedded Generators, Sri Lanka December 2000



Part 2: Protection and Operation of Grid Interconnection

Pae !5+o'tae at t.e Point of Common Coup'in s.ou'd be in accordance it. t.estatutor" 'imits&$on#statutor" 'imits ma" be areeab'e beteen CEB and t.e eneratincompan" if no ot.er customers are affected& (or e@amp'e, .ere t.e Point of Common Coup'in is remote from t.e Point of Supp'" it. a 'on 'ine t.at on'"ser)es t.e eneratin site or it. no direct connection of customers at t.e 'ine)o'tae&CEB reser)es t.e ri.t to re)ie and re)ise an" suc. non#statutor" 'imits& 7.eGeneratin Compan" s.a'' bear t.e costs resu'tin from an" suc. re)isions&

00 Po4er Fa#or Re:!re*e"#s7.e PP6 s.a'' specif" a poer factor for t.e connection t.is i'' be t"pica''"unit" but ma" be 'eadin <importin reacti)e poer=, dependin on )o'taereu'ation issues& It s.ou'd be noted t.at t.is specified )a'ue i'' be subHect tot.e to'erance of t.e enerator poer factor contro' unit&Pa"ments for reacti)e poer ma" be considered in t.e future, and are notco)ered in t.e Guide& 7.is i'' re4uire consideration of 'oss adHustments for acti)e poer e@port&It ma" be desirab'e to operate enerators in a )o'tae contro' mode to 'imit

)o'tae rise on distribution circuits, it. a 'ike'i.ood of conse4uent reacti)epoer imports& In t.is situation, t.e interaction of t.e enerator )o'tae contro's"stems i'' need to be considered .en t.ere is more t.an one enerator connected to a distribution 'ine&Simi'ar'", enerator poer output can be constrained to 'imit )o'tae rise under conditions of 'o feeder 'oad& 6ain, t.e interaction of poer or )o'taeconstraint contro' s"stems .ere t.ere is more t.an one enerator needs carefu'consideration&


Pae 20

3 EARTHING OF ELECTRICITY NET?OR@S AND E;BEDDED GENERATORS31 Ge"eralPub'ic e'ectricit" transmission and distribution netorks are connected or referenced to eart. as c'ose to t.eir ener" source as possib'e& Eart.in of netorks and t.e non#current carr"in meta'ork of p'ant and e4uipmentpro)ides a pre#determined pat. for t.e f'o of fau't current to operate protecti)ede)ices in t.e e)ent of a sin'e eart. fau't& ?.i'e it is possib'e to detect eart.fau'ts in uneart.ed netorks, protection discrimination and securit" in 'ares"stems is difficu't if not impossib'e&Disconnection of fau't" e4uipment is important to pre)ent daner and reducedamae from 'on#term o)er#)o'taes& Suc. o)er#)o'taes ma" be caused b" aninad)ertent contact it. a .i.er )o'tae s"stem or .en a transferred )o'taerise occurs in 'oer )o'tae netorks due to )o'tae rise of eart. s"stems s.ared

it. ot.er .i.er )o'tae netorks&7.e ke" reason for eart.in an" e'ectrica' s"stem and t.e connected p'ant is toreduce t.e risk of e'ectrica' s.ock and pre)ent unnecessar" damae& 7.edesin of eart.in s"stems for substations and p'ant in e'ectrica' netorks i''ac.ie)e t.is in t.e most economica' manner, and i'' be appropriate to t.e t"peof netork and its protection po'icies& Safet" re4uires co#ordination beteenfau't current manitude, t.e resu'tin )o'taes appearin in eart. s"stems andspeed of protection&$ote t.at t.e term 8+ is used for a'' )o'taes abo)e !000 +, to be consistentit. t.e ot.er sections of t.e Guide&Informati)e 6nne@ ! pro)ides additiona' detai's and e@p'anation of re4uirementsfor eart.in enerators connected to t.e CEB e'ectricit" netorks&

32 CEB Ele#r!!#y S77ly Ne#4or5sCEB e'ectricit" supp'" netorks ma" be connected to eart. at a sin'e point or atto or more points& 1u'tip'e netork eart.in ma" e@ist at a sin'e substation'ocation or at different points in t.e netork to faci'itate interconnections and



operationa' c.anes&7.e met.ods used to eart. t.e CEB distribution netorks are as fo''os:


Pae 2!• So'id eart.in of neutra' points of a'' transformer indins connected tonetorks .a)in an operatin )o'tae of !%2 k+ or .i.er&• Impedance eart.in or arc suppression coi' eart.in of transformer secondar" indins supp'"in netorks .a)in an operatin )o'tae of %% k+&• Impedance or so'id eart.in of transformer secondar" indins pro)idincustomer !! k+ supp'ies or supp'"in t.e CEB netork it. an operatin)o'tae of !! k+&• So'id eart.in of transformer secondar" indins pro)idin customer 'o)o'tae supp'ies or supp'"in L+ netorks&

30 Co*7a#!%!l!#y o Ne#4or5 a"$ Ge"era#or Ear#-!". 6rranements s.ou'd be areed to eart. t.e Embedded Generators s"stem in a

manner compatib'e it. t.e CEB supp'ies& (urt.ermore, appropriate enerator protection is re4uired to maintain safe conditions in t.e CEB netork s.ou'd itsnorma' eart. point become iso'ated or disconnected&7o accept additiona' points of netork eart.in suc. as enerator para''e'eart.in, CEB i'' consider t.e fo''oin tec.nica' issues: Contro''in manitude of eart. fau't current 1aintainin a predetermined pat. for eart. fau't current Detectin eart. 'eakae current Limitin circu'atin currents at fundamenta' and .armonic fre4uencies 6)oidin interference to communication s"stems ?.en appropriate, maintainin t.e effecti)eness of netork eart.in

33 Ge"era#or Parallel Ear#-!".?.ere a enerator is connected to t.e CEB %% k+ and !! k+ supp'" netorksand at risk of bein is'anded, t.e preferred met.od for safe operatin conditionsis for t.e enerator to be eart.ed at t.e PCC to t.e CEB 8+ supp'ies&Para''e' eart.in .en operatin in para''e' it. t.e CEB e'ectricit" supp'"netork i'' simp'if" and enera''" pro)ide safer enerator connections& 7o a''ot.is, CEB i'' consider t.e abo)e tec.nica' issues&


Pae 22?.i'e an eart.ed enerator or eart.ed transformer neutra' point i'' satisf" t.ebasic re4uirements for safet", t.e detai'ed desin of eart.in of eneratorsre4uires carefu' consideration&Lare enerators, <'arer t.an !1?= ma" be eart.ed .en operatin in para''e'

it. !!k+ or %%k+ netorks& 7.is i'' norma''" re4uire a neutra' eart.inimpedance of )a'ue to be areed& 7"pica''", t.is ma" be of t.e order ! pu toensure an ade4uate protection performance&7.e decision reardin eart.in of sma'' enerators .en operatin in para''e'it. pub'ic e'ectricit" netorks i'' take account of t.e cost of pro)idin t.eeart.in faci'it"& It is considered t.at enera''", it i'' be uneconomic for enerators sma''er t.an !1+6 to pro)ide para''e' eart.in faci'ities&se of a suitab'e transformer indin or t.e inter'ockin of sitc.es andautomatic eart.in of t.e enerator neutra' on'" .en t.e incomin mains aredisconnected ma" be re4uired to a)oid para''e' enerator eart.in& ?.ere aenerator is re4uired to operate independent'" of t.e CEB supp'ies, it must .a)ean eart. e'ectrode s"stem, .ic. s.ou'd be bonded to t.e CEB eart.in s"stemor termina', .ere)er t.is is a)ai'ab'e and practica'& 6'ternati)e'" .ere

permitted, a enerator ma" use a s.ared eart. s"stem&7.e areed met.od of eart.in a enerator s.ou'd ac.ie)e minimum risk toenerator p'ant, t.e supp'" netork it is connected to and operatin personne'&



CEB ma" decide t.at a enerator must not .a)e para''e' neutra' point eart.in.en operatin in para''e' it. t.e CEB supp'ies& In t.is case, appropriateprotection must ensure t.at an is'anded enerator is automatica''" disconnected&If an is'anded enerator ma" continue to operate and supp'" Loca' Capti)eLoads and some Line Capti)e Loads,• 7.e enerator>netork connection point ma" be appropriate'" para''e'eart.ed

.i'e t.e enerator operates&• 7.e netork at t.e Point of Common Coup'in ma" be automatica''" eart.ed

if is'anded&• 6ppropriate de)ices suc. as $eutra' +o'tae Disp'acement protection ma"be pro)ided to ensure safe conditions, and disconnect t.e enerator if aneart. fau't occurs in t.e CEB s"stem or t.e enerator s"stem&


Pae 2%?.ere a enerator is connected to t.e CEB L+ supp'" netork aa" from asubstation, t.e preferred met.od to ensure safe operatin conditions andremo)e risk of damae if neutra' conductors become open circuit, is for t.eenerator to operate it.out a para''e' neutra' eart. connection&Protecti)e de)ices must disconnect an is'anded enerator under t.is condition&?.ere a enerator is connected to t.e CEB L+ supp'" netork it. an on#sitesubstation and s.ou'd t.e netork be of 7$#C t"pe <.a)in mu'tip'e eart.edneutra' conductors=, t.e enerator ma" operate it. a para''e' neutra' eart.connection&7.e arranement must ensure t.at t.e connection of t.e enerator neutra' pointto t.e enerators eart. s"stem and t.e CEB eart. s"stem>termina' issubstantia', so'id, direct and c'ear'" identified&eu'ar c.ecks on t.e eart.in s"stem must be conducted b" t.e GeneratinCompan"&

3/ I"#ero""e#!o" o CEB a"$ Ge"era#or Ear#- Sys#e*sEart.in an e'ectricit" supp'" netork and a enerator s"stem re4uires t.e CEB

and enerator p'ant and e'ectrica' e4uipment to be connected to an eart. s"stemit. appropriate eart. e'ectrodes&?.ere)er netorks operatin it. different )o'taes are in c'ose pro@imit" andresistance areas of t.eir eart. s"stems o)er'ap, t.e o)er'appin eart. s"stemss.ou'd preferab'" be interconnected&In sma'' s"stems 'ike a enerator insta''ation, t.is i'' enera''" ac.ie)e t.e'oest practica' eart. resistance )a'ue and i'' minimise )o'tae differencesbeteen adHacent p'ants it. different operatin )o'taes&8+ metered supp'ies to enerator premises re4uire a combined 8+ eart.s"stem& 7.e 8+ eart. termina' i'' inc'ude an eart. connection to a CEB eart.e'ectrode s"stem and possib'" pro)ide a meta''ic pat. to t.e point .ere t.eCEB 8+ netork neutra' point is eart.ed&7.e enerator i'' .a)e to consider t.e possib'e effects of connectin enerator

s"stem 8+ and L+ eart. s"stems and ensure safe operatin conditions&L+ supp'ies to enerator premises from a dedicated, 'oca' CEB 8+>L+


Pae 2*transformer norma''" i'' .a)e independent 8+ and L+ eart. s"stems&If combined, t.e rise of )o'tae and t.e transferred )o'tae to t.e L+ neutra' s.a''be it.in acceptab'e 'imits&If independent'" eart.ed, t.e CEB L+ eart. termina' s.ou'd preferab'" beconnected to t.e Embedded Generators eart. s"stem&7.is i'' minimise t.e risk of damae to p'ant in t.e Embedded Generatorss"stem&7.e insu'ation of t.e supp'" transformer L+ indin and termina's must beade4uate to pre)ent daner from t.e rise of )o'tae on t.e 8+ eart. s"stem for



an eart. fau't in t.e supp'"in substation&7.e separation of t.e CEB 8+ and L+ eart. s"stem and t.e enerator eart.s"stem must be ade4uate to ensure t.at an" o)er'ap of t.e resistance areas of t.e to eart. s"stems does not cause daner&?.ere t.e CEB L+ eart. termina'>s"stem ma" not be made a)ai'ab'e to t.eenerator, t.e L+ connection i'' be of t.e 77 t"pe, it.out a meta''ic pat. to t.epoint t.e CEB L+ netork neutra' point is eart.ed&7.is i'' re4uire t.e CEB and t.e enerator eart. s"stem to .a)e an appropriateeart. 'oop resistance to ensure operation of protecti)e de)ices& CEB s.a''pro)ide to t.e Generatin Compan" t.e impedance of t.e part of t.e eart. 'oopt.at is it.in t.eir contro'&?.ere t.e separation of t.e CEB 8+ eart. s"stem and t.e enerator eart.s"stem is not ade4uate to ensure t.at an" o)er'ap of t.e resistance areas of t.eeart. s"stems is not sufficient to a)oid daner, t.en a'' eart. s"stems must beinterconnected& Eart. 'eakae protection s.a'' be insta''ed .ere t.e eart. fau'tcurrent is insufficient to operate o)er current protection&7.e desin of a'' eart. s"stems must ensure t.at a'' touc. and step )o'taes areit.in acceptab'e 'imits& 7ransferred )o'taes to Embedded Generators p'antmust not create unacceptab'e touc. and step )o'taes&Precautions must be taken to pre)ent damae and remo)e daner arisin from

transferred )o'taes to and from e@terna' meta''ic ser)ices and meta''ic pat.s&7"pica' eart.in arranements are s.on in 6nne@ !&


Pae 2-

3' Des!." o Ear#- Sys#e*sConnection to t.e enera' mass of eart. must be made usin an eart. s"stemand round e'ectrodes of ade4uate t.erma' and current carr"in capacit", anddimensioned to pro)ide and maintain reasonab'" constant eart. 'oop impedance,appropriate to t.e sensiti)it" of t.e insta''ed protection de)ices& Connection of a''p'ant to t.e eart. s"stem s.ou'd ensure appropriate bondin and s.ou'd a'so

maintain touc. and step )o'taes beteen and around eart.ed p'ant, inside andoutside of bui'dins, it.in acceptab'e 'imits& 6 CEB 8+ eart. faci'it" ma" not be effecti)e'" connected to 'oca' round andma" be subHect to sinificant )o'tae rise abo)e t.e potentia' of t.e enera' massof eart.& 7.is ma" occur .en eart. 'eakae current f'os for a 'oca' eart. fau'tor a fau't e'se.ere in t.e supp'" netork or in a .i.er )o'tae supp'" netork&?.ere)er an eart. termina' is a)ai'ab'e from t.e CEB, t.is s.ou'd be connectedto t.e enerator eart. s"stem to ensure t.e 'oest possib'e impedance returnpat. for eart. 'eakae currents to t.e point t.e supp'" netork is eart.ed&7.is i'' minimise )o'tae rise, reduce stress on insu'ation and norma''" i'' beade4uate to operate t.e Embedded Generators protecti)e de)ices&Contro' of resu'tin transferred )o'taes to enerator premises i'' be ac.ie)edb" t.e desin of t.e Embedded Generator eart.in s"stem and bondin of e@posed meta'ork on p'ant and e4uipment&In certain cases, CEB ma" re4uire t.e 'ocation to be c'assified appropriate'" for insertion of barrier faci'ities and safe iso'ation faci'ities in e@terna' meta''icser)ices, suc. as te'ecommunications it. meta''ic ires&Safet" re4uires comp'iance it. Eart.in Standards and prompt detection andiso'ation of eart. 'eakae currents& 7.e desin of an eart. s"stem must ensuret.at touc. and step )o'taes do not e@ceed )o'tae 'imits in t.e re'e)ant CEBdocuments or Standards appropriate to t.e disconnection times&


Pae 2/

/ S YNCHRONISATION OF GENERATORS/1 Ge"eralS"nc.ronisation means t.e minimisation of t.e difference in manitude,



fre4uenc" and p.ase an'e beteen t.e correspondin p.ases of t.e enerator output and t.e rid supp'" prior to t.e connection of t.e to supp'ies&S"nc.ronisation can be ac.ie)ed eit.er manua''" or automatica''", t.e 'atter bein preferab'e& It is )er" un'ike'" t.at ne insta''ations i'' inc'ude on'" manua's"nc.ronisation& If manua' s"nc.ronisation is suested for a particu'ar reason,its safe and re'iab'e operation s.ou'd be serious'" considered and imp'ementedcarefu''"&

/2 ol#a.e Fl#a#!o"Durin S"nc.ronisation of a sin'e enerator, t.e induced )o'tae f'uctuation ont.e rid s.ou'd not norma''" e@ceed % at t.e Point of Common Coup'in, ands.ou'd a'so meet t.e re4uirements of )o'tae step and f'icker i)en in Section !&

/0 Sy"-ro"os Ge"era#orsBefore a s"nc.ronous enerator can be connected to t.e rid, t.e enerator must be run up unconnected and its speed adHusted to s"nc.ronise t.eenerator output it. t.e rid supp'"&7.e )o'tae difference beteen t.e enerator output and t.e rid supp'" s.ou'da'so be minimised& It is usua' for t.e unconnected enerator )o'tae to be set afe )o'ts abo)e t.e t"pica' rid )o'tae& 6utomatic s"nc.ronisation is usua''" ac.ie)ed usin a contro' s"stem t.atincorporates contro' of t.e eneratin unit f ie'd and a o)ernor or an e'ectronic'oad contro' s"stem&

/3 Asy"-o"os Ge"era#ors 6s"nc.ronous enerators norma''" re4uire specia' measures to minimise t.einrus. current taken b" t.e enerator from t.e rid at t.e time of connection inorder to meet t.e )o'tae f'uctuation re4uirements of Section !!&Formatted: Bullets and NumberingFormatted: Bullets and NumberingFormatted: Bullets and Numbering


Pae 2

Suitab'e e4uipment and procedures ma" inc'ude: E'ectronic soft#start e4uipment esistance starter 1ec.anica''" dri)in t.e enerator up to near s"nc.ronous speedprior to connection&

// O#-er Ty7es o Ge"era#orsOt.er t"pes of enerators, .ic. i'' inc'ude static in)erters i'' need to .a)et.eir output s"nc.ronised it. t.e rid before or durin rid connection& 7.etransient c.aracteristics of t.e connection s.a'' be submitted to CEB&

/' Sy"-ro"!s!". C-e5 relay 6 s"nc.ronisin c.eck re'a" must be used to in.ibit t.e operation of t.eenerator connection breaker or contactor& 7.is re'a" i'' pre)ent connection of t.e enerator to t.e rid .en t.e to supp'ies are outside pre#set 'imits& 7.is

can be ac.ie)ed usin an e'ectrica' inter'ock&7"pica' re'a" settins i'' be:• ± 20 of p.ase an'e

• ma@imum difference in )o'tae of supp'ies of of t.e same nomina'

)o'tae

• ma@imum s'ip fre4uenc" 0&**

6 time de'a", t"pica''" 0&- to 2 seconds, on t.e operation of t.e re'a" iscommon'" used to ensure t.e s'ip fre4uenc" is it.in 'imits&S"nc.ronisin c.eck re'a"s ma" operate on a sin'e or a'' t.ree p.ases of t.esupp'ies& 6 sin'e p.ase re'a" i'' not be ab'e to c.eck for p.ase rotation of t.eto supp'ies& If a sin'e p.ase re'a" is used, t.en t.e p.ase rotation of t.e tosupp'ies must be c.ecked prior to first connection and fo''oin an"maintenance operations t.at in)o')ed disconnection of an" poer cab'in in t.e

s"stem&Formatted: Bullets and NumberingFormatted: Bullets and Numbering




Pae 23

' ISLANDED OPERATION

'1 Ge"eralIn t.e conte@t of embedded eneration, an is'anded netork i'' t"pica''"comprise of:i= 6 sin'e feeder or feeder section fo''oin a trip of t.e source circuit breaker or auto rec'oser&ii= 6 primar" netork or bus#section fo''oin a trip of t.e incomin circuitbreaker<s=&Embedded eneration and is'andin are defined in Section % of Part !&It .as been estab'is.ed t.at pro'oned is'andin is not acceptab'e, and .enceprotection is re4uired to detect t.e condition and trip t.e eneration it.in anacceptab'e time#frame&In enera', in an is'anded roup, t.ere i'' not be a stab'e ba'ance beteen 'oadand eneration resource& 8oe)er, it is possib'e, in a fe situations, t.at t.e

enerator and prime mo)er contro's can estab'is. a ne e4ui'ibrium beteenenerator<s= and 'oad in an is'anded roup&Protection to pre)ent is'andin is re4uired to detect an is'anded situation anddisconnect t.e enerator from t.e distribution 'ine&7.ere i'' a'so be a re4uirement for o)ercurrent and ot.er t"pes of enerator protection, .ic. are not specified in t.is Guide because suc. issues .a)e nosinificant imp'ications on t.e CEB s"stem&7.e se4uence of conditions prior to and durin is'andin are:Pre-islanded condition7.e acti)e and reacti)e poer outputs of t.e enerator are e@ported to t.e rid&7.e rid )o'tae and fre4uenc" are contro''ed b" t.e rid and t.erefore stab'econditions of )o'tae and fre4uenc" are ac.ie)ed&Initiating cause of islanding 7.ere are man" possib'e causes of is'andin but t.e" fa'' into to cateories:fau't or operationa'&


Pae 25In t.e case of an operationa' cause suc. as under#fre4uenc" trippin, t.e circuitdoes not see sinificant initiatin e)ent&Instant of islanding 6t t.e instant t.at is'andin occurs, t.ere is an instantaneous c.ane in t.epoer f'os of t.e is'andin circuit and outputs of enerators connected&Island operation(or stead"#state conditions to continue, t.e is'anded e'ectrica' eneration must

e4ua' t.e e'ectrica' 'oad <ne'ectin e'ectrica' storae .ic. is minima'=& Sincet.e probabi'it" of pre#is'anded eneration and 'oad bein e4ua' is e@treme'"un'ike'", t.en t.e poer imba'ance must cause an acce'eration or dece'eration of t.e rotatin p'ant in t.e is'anded netork and a resu'tin drift in fre4uenc"&

'2 Haar$s o Isla"$!".7.e potentia' .a9ards presented b" operatin a enerator in an is'andedsituation are:

• neart.ed operation of t.e distribution s"stem

• Loer fau't 'e)e's

• Out of s"nc.ronisation rec'osure

• +o'tae 'e)e's

• ;ua'it" of supp'"

• isk to maintenance personne'

'21 U"ear#-e$ O7era#!o" o #-e D!s#r!%#!o" Sys#e*



It is usua' for distribution 'ine s"stems to be eart.ed at t.e rid sub station on'",it. an 8+ de'ta uneart.ed arranement at t.e enerator connection& 7.is i''a'a"s be t.e case .ere mu'tip'e eart.in is not a''oed, as is t.e case in SriLanka at t.e time of ritin&?.en part of a distribution netork is disconnected from t.e rid sub stationeart. point, t.e uneart.ed s"stem i'' be enerised b" embedded eneratorsun'ess t.e enerators are disconnected b" is'andin protection& 7.e 'ine to eart.)o'taes of t.e t.ree p.ases ma" t.en drift, or in t.e case of a 'ine to eart. fau't,i'' be forced to s.ift& One p.ase i'' be referenced to eart. causin t.e ot.er p.ases to .a)e a p.ase to eart. )o'tae e4ua' to t.e nomina' p.ase to p.ase)o'tae& In t.is case, t.e norma' desin )o'tae 'imits for insu'ation and ot.er e4uipment ma" be e@ceeded& 7.is ma" cause damae or cause a .a9ard&Formatted: Bullets and NumberingFormatted: Bullets and Numbering


Pae %07.is situation can be detected usin a $eutra' +o'tae Disp'acement re'a", see

Section and 6nne@ %&'22 Lo4er Fal# Le&els7.e fau't 'e)e' of an is'anded s"stem is 'ike'" to be 'oer t.an t.e minimum fau't'e)e' of t.e rid sub station durin norma' operation& 7.is means t.at t.e settinsof protection re'a"s ma" be inade4uate to protect t.e is'anded netork&Detai's on t.e consideration of a c.ane in fau't 'e)e's and its effects are i)en inSection !0&'20 O# o sy"-ro"!sa#!o" relosreIn t.e period fo''oin t.e initiation of is'andin, a p.ase difference arisesbeteen t.e rid and is'anded side of t.e iso'atin circuit breaker or rec'oser&7.e rid and is'anded netork are said to be Jout of s"nc.ronism& If t.e circuitbreaker or rec'oser rec'oses before t.e enerator is disconnected, t.en a se)eresure of current ma" f'o beteen t.e rid and t.e enerator, causin se)ere)o'tae disturbances& 7.e e)ent can cause se)ere mec.anica' s.ock to t.eenerator and prime mo)er, and t.ere is risk of damae to t.e enerator ande4uipment on t.e e'ectrica' s"stem&Out of s"nc.ronisation connection ma" be a)oided b" t.e use of dead 'ine c.eckor s"nc. c.eck faci'ities of t.e rid sub station breakers& See Section &'23 ol#a.e Le&els7.e operation of a enerator supp'"in a distribution feeder in an is'andedsituation ma" cause t.e s"stem )o'tae 'e)e's to be outside norma' operatin or statutor" 'imits&7.e )o'tae i'' be determined b" t.e output of t.e embedded enerators .ic.are primari'" desined for connection to t.e rid and ma" be operatin in poer factor contro' mode it. 'itt'e contro' of output )o'tae&7.e enerator )o'tae protection 'imits of nomina' ±!0 ma" not protectconsumers from )o'tae e@cursions substantia''" outside statutor" 'imits but i''

'imit t.e duration for comp'iance it. BS E$ -0!/0&Formatted: Bullets and NumberingFormatted: Bullets and NumberingFormatted: Bullets and Numbering


Pae %!'2/ al!#y o S77ly7.e is'anded netork i'' .a)e a sinificant'" 'oer fau't 'e)e'& 7.is is 'ike'" toincrease t.e )o'tae f'uctuations durin t.e period of is'andin, caused b"consumer e'ectrica' e4uipment&'2' R!s5 #o ;a!"#e"a"e Perso""el

7.e connection of a enerator to a distribution 'ine t.at .as been disconnectedfrom t.e rid for t.e purposes of maintenance or repair ma" cause .arm topersonne' t.rou. t.e enerisation of a 'ine t.at is e@pected to be dead&



6'' 'ines must be considered as possib'" enerised from remote sources and adistribution 'ine t.at .as been disconnected for maintenance or repair s.ou'd.a)e temporar" eart.in app'ied to t.e 'ine before an" ork is undertaken& 7.isou'd be part of norma' procedures&

'0 Co**o" Case Tr!77!".'01 Ge"eral

Common Cause <or Common 1ode= trippin is .ere an e)ent .ic. causes arid disturbance 'eads to t.e trippin of se)era' enerators, some of .ic. ma"be on separate distribution 'ines from t.e one .ere t.e fau't occurred&'02 R!s5s #o #-e Ne#4or5Studies b" t.e CEB, and e@perience from ot.er countries, indicates t.at in SriLanka t.e risks to t.e rid netork of t.e 'oss of eneration can be c'assified as:• Loss of a sin'e enerator or site it. a ma@imum eneration capacit" of 'esst.an !01? s.ou'd .a)e no sinificant effect on rid netork if t.econnection meets )o'tae step re4uirements&• Loss of mu'tip'e enerators or sites it. a ma@imum eneration capacit"tota''in beteen !0 1? and -01? i'' cause 'oca' )o'tae disturbancesand possib'e instabi'it" of ot.er eneratin p'ants&• Loss of mu'tip'e enerators it. a ma@imum eneration capacit" tota''inbeteen -01? and !001? i'' cause sinificant rid fre4uenc" dip and

possib'e under#fre4uenc" trippin of feeders& nder 'o demand conditions,it ma" a'so trier a tota' fai'ure of t.e CEB rid&• Loss of mu'tip'e enerators it. a ma@imum eneration capacit" tota''inreater t.an !001? is 'ike'" to cause rid instabi'it" resu'tin in possib'etota' fai'ure of CEB rid&Formatted: Bullets and NumberingFormatted: Bullets and NumberingFormatted: Bullets and NumberingFormatted: Bullets and Numbering


Pae %2

$ote t.at t.e 'e)e's of eneration defined .ere are subHect to c.ane as t.e rideneration and 'oads c.ane in t.e future&7.e 'oss of a sin'e enerator in t.e scope of t.e Guide is not sinificant for t.eoperation, stabi'it" or securit" of t.e rid& 8oe)er, common cause trippin of man" enerators ma" .a)e serious conse4uences for t.e CEB rid&(re4uent spurious trippin of eneration can a'so .a)e a sinificant financia'impact on t.e enerator .ic. ma" inf'uence t.e economic se'ection of is'andinprotection met.od&Ot.er dispatc.ed enerators i'' co)er t.e disconnection and ma" a'so burnunnecessar" fue' .ence tota' cost to CEB ma" be more t.an t.is&'00 R!s5s #o #-e Ge"era#or 7.e conse4uence of e@cessi)e and unanted trippin to t.e enerator is most'"financia' due to t.e unnecessar" 'oss of eneration& 7.ere ma" a'so be an affect

on mec.anica' and e'ectrica' e4uipment 'ife in t.e case t.at trips are occurrindai'"&

'3 Sores o Co**o" Case Tr!77!". o Ge"era#ors7.e fo''oin de)ices and conditions are identified and assessed as possib'ecauses of common cause trippin:Loss of mains re'a"s are t.e main possib'e cause of common cause trippin of eneration& 7.e a)oidance of common mode trippin is t.erefore a maHor consideration of Section on 'oss of mains detection met.ods&'31 Loss o ;a!"s RelaysIt is difficu't for protection re'a"s to distinuis. beteen 'oss of mains e)ents andenera' rid disturbances .ic. ma" cause Knuisance or unnecessar" trippin&7.is is co)ered in detai' in Section&'32 ol#a.e RelaysIt is improbab'e t.at non#fau't )o'tae e@cursions i'' e@ceed ±!0 for more t.an

0&- second& Suc. an e)ent ou'd a'so resu't in substantia' 'oss of motor 'oad,offsettin some 'oss of eneration&Formatted: Bullets and Numbering



Formatted: Bullets and NumberingFormatted: Bullets and NumberingFormatted: Bullets and Numbering


Pae %%'30 Fre:e"y RelaysIt is un'ike'" t.at enera' non#is'anded fre4uenc" e@cursions i'' e@ceed M*,and #/, un'ess t.ere is a condition under .ic. trippin of embeddedeneration ou'd .a)e no furt.er impact&'33 Loal Ge"era#or I"s#a%!l!#y 6 fau't at or c'ose to t.e primar" busbars or on t.e 'oca' transmission s"stem,cou'd resu't in po'e s'ippin of one or more enerators on t.e distributionnetork& Po'e s'ippin can cause damae to t.e enerator, and it. 'arer mac.ines, i'' cause e@tensi)e current sures or sins and se)ere customer )o'tae f'uctuations& 7.is in turn cou'd cause trippin of ot.er embeddedenerators&7.e potentia' for po'e s'ippin of 'are enerators s.ou'd t.erefore be assessed

and protection pro)ided if t.e risk is confirmed& It is recommended t.atenerators abo)e -1? s.ou'd be pro)ided it. po'e s'ip protection or assessedto confirm t.at t.is is not re4uired&Formatted: Bullets and NumberingFormatted: Bullets and Numbering


Pae %*

8 ISLANDING DETECTION AND PROTECTION

81 Ge"eralProtection re'a"s s.ou'd be used to detect abnorma' e'ectrica' conditions on t.erid .ic. ma" indicate t.at an is'anded condition .as occurred& 7.e" ma" a'soindicate t.at t.e rid s"stem is, for some ot.er reason, outside operatinconditions, and embedded enerators s.ou'd be disconnected& 6fter a distribution 'ine, to .ic. an Embedded Generator is attac.ed, isdisconnected from a rid substation, t.ere i'' be some disturbance in t.ee'ectrica' condition on t.e distribution 'ine& 7.is disturbance ma" take t.e form of,• a c.ane in )o'tae or fre4uenc" or • a sin'e s.ift in t.e )o'tae )ector or • a c.ane in reacti)e poer f'o&7.e stand#a'one detection of an is'anded situation is based upon t.e detection of t.is e'ectrica' disturbance&7.e manitude and t"pe of disturbance i'' depend upon t.e t"pe and capacit"of t.e eneratin p'ant, t.e distribution 'ine and transformer c.aracteristics, andt.e nature of t.e connected 'oads&

If at t.e time of disconnection,• t.e remainin connected 'oad and enerated poer are in ba'ance a"$

• t.e feeder reacti)e poer demand and enerated reacti)e poer are in

ba'ance a"$

• t.e feeder 'ine to eart. capacitance are e4ua' for a'' p.ases,

t.en t.ere i'' be no disturbance on t.e 'ine and t.ere i'' be no immediate a",apart from detection of t.e c.ane of fau't 'e)e', to detect an is'anded situation&7.is ba'anced Embedded Generator and 'oad situation is e@treme'" un'ike'" tooccur&


Part 2: Protection and Operation of Grid InterconnectionPae %-

82 Isla"$!". De#e#!o" Sys#e*s a"$ Se##!".s



821 Ge"eral7.e t"pes of protection re'a"s and recommended settins t.at are to be used todetect an is'anded situation are 'isted in t.e fo''oin subsections&?it. t.e e@ception of t.e )o'tae and fre4uenc" t"pes <&2&2 and &2&%= t.eprotection is knon as Loss of 1ains protection& 6 description of t.e operation and use of t.e Loss of 1ains protection is i)en in 6nne@ 2&7.e settins of re'a"s s.ou'd be areed it. CEB and t.e settins s.a'' not bec.aned it.out t.e e@press areement of CEB&It must be noted t.at t.e tota' trippin time i)en under eac. t"pe of protectioninc'udes an" interation or timin period of t.e protection re'a" as e'' as re'a"and circuit breaker operatin times&822 O&er a"$ U"$er ol#a.e7.e )o'tae of eac. p.ase is monitored and an" e@cursions outside preset 'imitson an" one p.ase s.ou'd cause t.e re'a" to operate&7.e re'a" s.ou'd .a)e time de'a" of operation based on it bein 'on enou. toa)oid spurious trips due to remote fau'ts, but s.ort enou. to ensuredisconnection before out of s"nc. rec'osure&SettinsLe)e' for 8+ point of connection: ± !0

Le)e' for L+ point of connection: M!0, #!* of nomina' 2%0 +$ote: 'imits s.ou'd not e@ceed or be 'ess t.an t.e ma@imum and minimumstatutor" )o'tae b" more t.an a fe percent and s.ou'd be based on dec'arednomina' )o'tae=7ota' trippin time s.a'' be 'ess t.an 0&- second&In some cases, t.e tota' trippin time ma" be increased b" areement beteenCEB and t.e Generatin Companies&820 O&er a"$ U"$er Fre:e"y7.e fre4uenc" on a sin'e p.ase is monitored and an" e@cursions outside preset'imits i'' cause t.e re'a" to operate&Formatted: Bullets and NumberingFormatted: Bullets and Numbering


Pae %/SettinsLe)e'M * , #/ <i&e& -2 89 to * 89=7.is rane .as been se'ected on t.e basis t.at t.e" are outside t.e norma'rane of fre4uenc" )ariation of t.e rid but c'ose enou. to nomina' fre4uenc" toa''o trippin of enerator in is'anded mode&It ma" be possib'e for t.e 'o fre4uenc" to be reduced to */ 89 i)en t.epossibi'it" of rid reco)er" from */ 89& 7.is i'' need to be confirmed it. CEB& 6dditiona' enerator 'o fre4uenc" protection ma" be re4uired to ensure t.att.ere is no damae to t.e enerator at 'o fre4uenc"&

7ime de'a"7.ere is no re4uirement for a time de'a"&7ota' trippin time s.a'' be 'ess t.an 0&- second&823 Ra#e o C-a".e o Fre:e"yoCo( re'a"s operate b" measurin t.e 9ero crossins of successi)e s'idinc"c'es <or indos= of t.e measured )o'tae, estab'is.in t.e apparent rate of c.ane of fre4uenc" <oCo(= and detectin .en t.e app'ied settin ise@ceeded& Some oCo( de)ices detect a cumu'ati)e anu'ar s.ift and are a'sosensiti)e to initia' c.ane or )ector s.ift of t.e measured )o'tae& See 6nne@ 2for detai's of Ktrue oCo(&7rue oCo( detects t.e is'anded condition rat.er t.an its onset or pre#condition&It is unab'e to distinuis. nationa' rid and 'oca' is'andin e)ents&SettinsK7rue oCo( operation is specified for some situations in Section 3&

Limits:2&- 89>second 7.is .as been specified to ensure t.ere is minimum spurious



trippin&7ime de'a"7.ere is no re4uirement for a time de'a"&7ota' trippin time s.a'' be 'ess t.an 0&- second&82/ ol#a.e e#or S-!#+ector s.ift re'a"s operate b" measurin .a'f c"c'e )o'tae and detectin a stepc.ane e@ceedin an e4ui)a'ent )ector s.ift settin& It detects a )o'tae )ector


Pae %s.ift arisin .en t.ere is a step c.ane in t.e current t.rou. t.e enerator interna' impedance& Suc. a condition i'' be caused b" a fau't or t.e onset of is'andin&+o'tae +ector S.ift is in.erent'" a protection to disconnect a enerator fromdisturbances and is susceptib'e to spurious trippin durin fau'ts because itdetects )o'tae an'e disturbance rat.er t.an t.e c.aracteristic of t.e is'andedcondition&


Pae %3SettinLe)e'/o in a .a'f c"c'e& 7.is can be de#sensitised to up to !2 o .ere spurious trippinis e@perienced&7ime de'a"7.ere is no re4uirement for a time de'a"&7.e ma@imum tota' trippin time s.a'' be 'ess t.an 0&- second&82' Re&erse ARse)erse +6 re'a"s operate b" detectin a f'o of reacti)e poer from t.e

enerator into t.e rid& 7.e tec.ni4ue depends on t.e is'anded netork .a)int.e t"pica' net +6 demand and t.e enerator .a)in a norma' operatinreacti)e poer demand <i&e& t.e poer factor contro''er is set 'eadin=&e)erse +6 protection can pro)ide a simp'e and re'iab'e met.od of is'andindetection .en t.ere is on'" a sin'e enerator connected to a distribution 'ineand .ere ot.er conditions are suitab'e& 7.e Capti)e Line Load must .a)e a +ar demand .ic. cannot be met b" ot.er s"stem components suc. as cab'es andcapacitors&Generators must .a)e stab'e poer factor contro' to enab'e re)erse +6protection to be used& 7.e enerator s.a'' be importin reacti)e poer under norma' operation&7rippin must be de'a"ed to a)oid 'oss of eneration durin s.ort )o'tae dips<due to fau'ts= or transient e@cursions of t.e poer factor contro''er <especia''"

fo''oin s"nc.ronisation or )o'tae disturbances=&SettinLe)e'7.is is to be areed beteen t.e Generatin Compan" and CEB& 7"pica''"'e)e's of !#- of t.e manitude of t.e ma@imum e@port k? ma" be used& 7.esettin i'' be dependent upon t.e enerator and 'oca' 'oad conditions&7ime de'a"7.e 'esser of up to - seconds or -0 of t.e time de'a" of auto rec'ose de)ices&828 I"#er#r!77!".Intertrippin is a direct means of is'andin protection, .ic. pro)ides a re'iab'emet.od of trippin is'anded enerators it.out an" unanted common cause


Pae %5



prob'ems& It is t.erefore recommended .ere practica' for 'arer enerators <seeSection 3 for protection re4uirements=&It operates b" sendin a trip sina' from t.e circuit breaker or rec'oser responsib'e for t.e is'andin, to a'' t.e enerators .ic. use t.is met.od as t.e'oss of mains protection&7.e re'iabi'it" of intertrippin is dependent on t.e securit" of t.e transmissionmet.od& Pi'ot ires, pub'ic te'ep.one, radio or sate''ite communications arepossib'e but t.e re'iabi'it" s.ou'd be assessed on an indi)idua' basis&+o'tae barriers ma" be re4uired on communication pat.s& Consideration mustbe i)en to t.e routin of intertrip sina''in, to minimise t.e risk of interference,particu'ar'" durin 'ine fau't conditions& 7.e communication 'ink s.ou'd bere'iab'e and fai'#safe& If t.e communication 'ink fai's, t.e enerator s.ou'dautomatica''" trip&82 Fal# T-ro4er 7.is is a specia' app'ication of a fau't t.roer& It is a form of intertrippin usint.e p.ase conductors as t.e medium for communication& 7.e fau't t.roer ou'dbe insta''ed at t.e source substation and ou'd be operated fo''oin openin of an appropriate source circuit breaker& 7.e de)ice ou'd eit.er put a s.ort circuiton t.e is'anded feeder, creatin detectab'e o)er current or under)o'tae andcausin operation of enerator protection, or it cou'd put an eart. fau't on one

p.ase, causin t.e operation of enerator $+D&Operation ou'd be de'a"ed to a''o enerator re'a"s to operate if sufficient 'oadimba'ance e@ists&It ou'd on'" be effecti)e for enerators connected beteen t.e source breaker and t.e first auto rec'oser&829 Res#ora#!o" 6'' re'a"s s.ou'd .a)e a minimum restoration time of one minute after t.e CEBrid supp'" is restored to be it.in specified 'imits&8216 F#re De&elo7*e"#s7.e Guide does not prec'ude t.e use of no)e' met.ods of ac.ie)in adependab'e and re'iab'e 'oss of mains function in t.e conte@t of t.e CEB


Pae *0netork& 6n e@amp'e of a possib'e option is t.e use of sensiti)e true oCo(b'ocked b" )ector s.ift to pre)ent operation durin enera' rid instabi'it"&

80 Isla"$!". Ne#4or5 Pro#e#!o"801 Ge"eral7.e primar" protection specified in t.e Guide is desined to detect t.e is'andincondition and trip t.e embedded enerators it.in a safe period&Detection of t.e is'anded condition is not possib'e in a'' cases, especia''" .ent.e 'oad ma" c'ose'" matc. t.e eneration on t.e is'anded netork&Secondar" protection suc. as dead 'ine and s"nc. c.ecks on auto rec'osinde)ices and neutra' )o'tae disp'acement <$+D= re'a"s is recommended asback#up in cases .ere 'oss of mains protection is not ade4uate'" dependab'e toprotect aainst t.e more se)ere and 'ike'" conse4uences of is'andin&In addition, automatic 'o fre4uenc" disconnection re'a"s on feeders it. ana)erae net e@port capabi'it" s.a'' be rendered inoperati)e& 7.e cumu'ati)eeneration capabi'it" of a feeder s.a'' be updated and compared to metered'oads& 7.is information s.a'' be used to ensure t.at t.e current f'o .enrestorin a tripped feeder is it.in t.e feeder and protection capabi'it"&802 I"-!%!#!". o Relose De&!es7o standard met.ods are a)ai'ab'e to pre)ent c'osure of a circuit breaker or rec'oser onto a 'i)e or out of s"nc.ronised circuit,• )o'tae restraint <dead 'ine c.eck=, a"$or • s"nc. c.eck re'a"In most app'ications, t.e dead 'ine c.eck i'' be ade4uate for radia' 'ines, sincet.e probabi'it" of pro'oned is'anded operation is e@treme'" sma''&

Dead 'ine c.eck re'a"s in.ibit automatic or manua' circuit breaker c'osure onto a'i)e circuit& 7.is is not is'andin protection and t.erefore does not rep'ace 'oss of mains or ensure a safe is'anded condition& 8oe)er, it does mitiate t.e risk of



is'andin if 'oss of mains does not operate&7.is is a simp'e and dependab'e met.od of pre)entin out of s"nc. c'osure.ere 'oss of mains protection is not secure&Formatted: Bullets and Numbering


Pae *!Po'e mounted rec'osers ma" need to be rep'aced b" ne de)ices& 7.e cost of addin a )o'tae re'a" to t.e source breaker contro' circuit is enera''"sinificant'" 'ess&800 Ne#ral ol#a.e D!s7lae*e"# (ND) Pro#e#!o" 6n $+D sc.eme measures t.e disp'acement of t.e neutra' on t.e 8+ side of t.eenerator transformer and operates it. de'a" .en t.e disp'acement [email protected] trip settin& 7.is de)ice does not detect is'andin, its purpose is to detect aneart. fau't and an unsafe is'andin condition&$+D is a dependab'e means of satisf"in safet" re4uirements and mitiatin t.erisk of is'andin .en enerators operate it.out para''e' eart.in&$+D is imp'emented b" .a)in t.ree )o'tae transformers <+7s= on t.e primar",

8+, side of t.e connection transformer .ic. are connected p.ase to round& If 8+ meterin )o'tae transformers are a)ai'ab'e, t.ese ma" be of an appropriatet"pe and ma" be uti'ised to reduce t.e incrementa' cost&7.e detection re'a" i'' be used to trip eit.er an 8+ or L+ breaker to disconnectt.e enerator from t.e 'ine&+o'tae transformers pro)idin $+D protection i'' re4uire a )o'tae factor of !&5& 7.e time ratin under )o'tae factor i'' depend on t.e t"pe of s"stemeart.in at t.e Grid or Primar" CEB substation and t.e fau't c'earance time of t.e $+D protection s"stem&7.e $+D protection s.ou'd rade it. t.e eart. fau't protection at t.e CEB Gridor Primar" substation, so t.at feeder eart. fau'ts are c'eared at t.e CEBsubstation before $+D protection in ot.er feeders operate& In case of 6rcSuppression Coi' <6SC= eart.in, t.e 6SC s.ou'd not be a''oed to maintain an

eart. fau't for a 'on time& It s.ou'd be s.orted#out in a fe seconds and t.eeart. fau't protection in t.e fau't" feeder a''oed to c'ear t.e fau't& 7.e $+Ds.ou'd rade it. t.e operation of t.is eart. fau't re'a"&7.e $+D re'a" s.ou'd be capab'e of it.standin t.ree times t.e secondar"p.ase )o'tae of t.e )o'tae transformer& (urt.er detai's of $+D protection arei)en in 6nne@ %&SettinLe)e'7"pica''" 2- of p.ase )o'tae on effecti)e'" rounded s"stems


Pae *27.is settin ma" need to be increased for impedance eart.ed s"stems to a)oidtrippin on distant eart. fau'ts&7ime de'a"! to % seconds dependin on speed of 'ine eart. fau't protection on ot.er feeders&


Pae *%

I;PLE;ENTATION OF ISLANDING PROTECTION

1 Ge"eral

Protection re'a"s s.a'' be of suitab'e 4ua'it" to pro)ide re'iab'e and consistentoperation& 7.e performance 'e)e's of t.e re'a"s s.a'' be dec'ared b" t.emanufacturer&



It is preferab'e to use pro)en protection e4uipment supp'ied b" a reputab'emanufacturer it. a track record in t.is t"pe of app'ication& 7.e performance of a'' protection re'a"s s.a'' be it.in t.e scope of IEC protection product fami'"Standard IEC /02-- <former'" IEC 2--=&It is recommended t.at contro' and protection pane's are soak tested <i&e& t.eprotection re'a" pane's are enerised for se)era' .ours or da"s= prior to beinput into operation& Durin t.e soak test t.e operation of t.e protection re'a"ss.ou'd be c.ecked periodica''"&Protection re'a"s and t.e associated sensin circuits must be desined tomaintain accurac" and operation in fau't conditions& Particu'ar considerations.ou'd be made of t.e re4uirements for current transformers to sustain operation.en fau't currents occur& Current and )o'tae transformers s.ou'd beappropriate'" se'ected and comp'" it. product standards IEC /0!3- <former'"IEC!3-= and IEC /0!3/ <former'" IEC !3/= respecti)e'"& 6'' protection re'a"s to .a)e indication of operation&It is usefu' if t.e re'a" s"stem can indicate .ic. re'a" or function operated firstto disconnect a enerator durin a fau't condition& 7.e indication ma" be reset atne@t breaker or contactor c'osure& 7.is indication is not a re4uirement&Secondar" inHection test points s.ou'd be pro)ided .ere practica' to faci'itatecommissionin and 'ater testin of re'a" settins and operation&

2 I"#ero""e#!o" Pro#e#!o" Re:!re*e"#sIn order to specif" t.e t"pe of interconnection protection re4uired, EmbeddedGenerator interconnections ma" be c'assified into one of fi)e cases& 7.eprotection re4uirements for t.ese fi)e cases are i''ustrated in (iures * to &Formatted: Bullets and Numbering


Pae ** 6 summar" of t.e Case definitions and protection re4uirements is s.on in t.efo''oin tab'e& 7.e Cases are described subse4uent'"&S**ary o ;!"!** Pro#e#!o" Re:!re*e"#s or

E*%e$$e$ Ge"era#or I"#ero""e#!o"Case 1 Case 2 Case 0 Case 3 Case /Generator t"pe 6'' 6'' See Case %description 6'' See Case -descriptionSe'f commutatedstaticin)erters1inimumcapti)e 'oad

L L L L1a@imumcumu'ati)einsta''edcapacit"

N0&- @ L N0&3 @ L 0&3 @ L 0&3 @ L1a@imumsite insta''edcapacit"

N - 1? N - 1? N - 1? - 1?nder ando)er )o'taeprotection

• • • • •nder and



o)er fre4uenc"protection

• • • • •+ector s.iftprotection

• • •OCO(protection

K7rueOCO(protection

$+Dprotection

• <!=

Intertrippin Loss of

P.ase• • • • • •Ot.er

• 1andator" minimum re4uirement

* (or ot.er re4uirements and a'ternati)es see t.e descriptions under t.e respecti)ecase descriptions and re4uirements<!= $+D or para''e' eart.in7.e abo)e tab'e summarises on'" t.e mandator" re4uirements of protection& Ot.er mandator" re4uirements are described e'se.ere in t.e Guide&


Part 2: Protection and Operation of Grid InterconnectionPae *-21 Case 1Ge"era#or Ty7e 6'' t"pes&Co"$!#!o"s

• 7.e insta''ed eneratin capacit" is less t.an .a'f t.e minimum Capti)e Load

<see note be'o=, and

• 7.e insta''ed eneratin capacit" is 'ess t.an - 1?&

Note: Minimum Captive Load is the sum of Minimum Captive Line Load and theMinimum Captive Local Load. The minimum Captive Line Load may be difficult to establish in !hich case it may be assumed to be "#$ of average line load.In t.is case, fo''oin distribution 'ine disconnection, t.e Embedded Generator

speed and )o'tae i'' fa'' rapid'" as t.e enerator<s= i'' be unab'e to supp'" t.e'oad&Pro#e#!o" Re:!re$nder and o)er )o'taender and o)er fre4uenc"O7#!o"al, a# #-e D!sre#!o" o #-e Ge"era#!". Co*7a"y7.ree p.ase )ector s.iftDes!." Cr!#er!a7.e minimum Capti)e Load is subHect to c.ane due to insertion of sectiona'isers, rec'osers, reconfiuration or reduction in customer 'oad& CEBs.a'' be informed an" modification made to t.e Embedded Generator for re)ie,and to assess t.e need for an" retrospecti)e en.ancement of protection&Simi'ar'", .ene)er an" c.anes to t.e CEB s"stem affects t.e Capti)e LineLoad, CEB s.a'' re)ie t.e interconnection protection and ad)ice t.e Generatin

Compan" accordin'"& 6uto rec'osers must .a)e a minimum rec'ose time of ! second to minimise t.e



possibi'it" of out of s"nc. rec'osure& CEB s.a'' )erif" t.at t.is rec'osin time isade4uate for interconnection protection to operate prior to rec'osin&


Pae */(iure!


Pae *22 Case 2Ge"era#or Ty7e 6'' t"pesCo"$!#!o"s

• 7.e insta''ed eneratin capacit" is less t.an 30 of t.e minimum Capti)e

Load <see note be'o=, and


Note: Minimum Captive Load is the sum of Minimum Captive Line Load and theMinimum Captive Local Load. The minimum Captive Line Load may be difficult to establish in !hich case it may be assumed to be "#$ of average line load.Pro#e#!o" Re:!re$nder and o)er )o'taender and o)er fre4uenc"%#p.ase )ector s.iftO7#!o"al, a# #-e D!sre#!o" o CEB, 4-e" a %ala"e %e#4ee" Ca7#!&e Loa$a"$ #-e !"s#alle$ .e"era#!". a7a!#y !s &ery l!5ely #o or 7rue oCo( ma" be used as e'' as )ector s.ift&Des!." Cr!#er!a 6s per Case !&


Pae *3fiure2


Pae *520 Case 0Ge"era#or Ty7e

6'' t"pes e@cept mains e@cited enerators defined in Case -&Co"$!#!o"s<

• 7.e insta''ed eneratin capacit" is *ore t.an 30 of t.e minimum Capti)e

Load <see note be'o=, suc. t.at 'oad>enerator ba'ance is possib'e, and


Note: Minimum Captive Load is the sum of Minimum Captive Line Load and theMinimum Captive Local Load. The minimum Captive Line Load may be difficult to establish in !hich case it may be assumed to be "#$ of average line load.Pro#e#!o" Re:!re$nder and o)er )o'taender and o)er fre4uenc"%#p.ase )ector s.ift$+D

Dead#'ine c.eck<Ktrue oCo( ma" be used in p'ace of )ector s.ift=



or as a rep'acement for t.e combination of +ector s.ift and $+D, an" one of t.efo''oin ma" be used:Intertrippin(au't t.roine)erse +6 protection it. s"nc.ronous enerators, .ere on'" oneenerator is connected to t.e circuit&$+D protection is not re4uired .ere t.e ma@imum site insta''ed capacit" is 'esst.an !1?, if t.e cumu'ati)e embedded eneratin capacit" on a distribution 'inet.at does not .a)e $+D protection is 'ess t.an 0&3 times t.e minimum capti)e'oad&7.e fittin of dead'ine c.eck re'a"s on upstream breakers or sectiona'isers, or disab'in of a'' upstream automatic rec'osin de)ices s.ou'd be considered&Des!." Cr!#er!a7.e tota' eneration connected to a sin'e rid substation usin t.e )ector s.iftmet.od for 'oss of mains protection s.a'' not e@ceed 201?& 7.is is to pre)entpossib'e common cause trippin of 'oca' eneration e@ceedin % of CEB ridminimum 'oad& 7.is 'imit i'' be increased it. t.e increase in rid minimum'oad& ?.ene)er an" c.anes to t.e CEB s"stem affects t.e Capti)e Line Load,CEB s.a'' re)ie t.e interconnection protection and ad)ice t.e GeneratinCompan" accordin'"&


Pae -0(iure %


Pae -!23 Case 3Ge"era#or Ty7e

6'' t"pesCo"$!#!o"s7.e insta''ed eneratin capacit" of an Embedded Generation site is reater t.an - 1?&Co"!.ra#!o"It is preferred t.at t.e Embedded Generator is connected direct'" to t.e primar"bus rat.er t.an teed into an 8+ distribution feeder&Pro#e#!o" Re:!re$nder and o)er )o'taender and o)er fre4uenc"Intertrippin from rid substation bus intakePara''e' eart.in or $+D protectionIf t.e Embedded Generator is teed into a distribution feeder, t.e fo''oin is a'so

re4uired:Intertrippin from feeder breaker or (au't t.roinor e)erse +6 protection, if app'icab'e&Des!." Cr!#er!aGenerators 'arer t.an - 1? i'' be encouraed to obtain more secureconnections& Insecurit" is main'" a factor of t.e 'ent. and e@posure of o)er.ead'ines to 'i.tnin and )eetation& (or 'are enerators remote from t.e primar"bus, ade4uate securit" ma" on'" be ac.ie)ed b" doub'e circuit connection to t.eprimar" bus&




Pae -2fiure *


Pae -%2/ Case /Ge"era#or Ty7e1ains e@cited as"nc.ronous enerator it. 'oca' poer factor correction 'esst.an t.e reacti)e poer demand, or a 'ine commutated in)erter&7.e CEB netork>circuit capacitance is not sufficient to se'f e@cite t.e enerator&Co"$!#!o"s

• 7.e insta''ed eneratin capacit" is *ore t.an 30 of t.e minimum Capti)e

Load <see note be'o=, suc. t.at 'oad>enerator ba'ance is possib'e, and• $o s"nc.ronous eneration or se'f#e@cited eneration are connected&Note: Minimum Captive Load is the sum of Minimum Captive Line Load and theMinimum Captive Local Load. The minimum Captive Line Load may be difficult to establish in !hich case it may be assumed to be "#$ of average line load.

Pro#e#!o" Re:!re$nder and o)er )o'taender and o)er fre4uenc"%#p.ase )ector s.iftDes!." Cr!#er!a7.e tota' eneration connected to a primar" substation usin t.e )ector s.iftmet.od for 'oss of mains protection s.a'' not e@ceed 201?& 7.is is to pre)entpossib'e common mode trippin of 'oca' eneration e@ceedin % of CEB ridminimum 'oad& 7.is 'imit s.ou'd be increased it. t.e increase in rid minimum'oad&


Part 2: Protection and Operation of Grid InterconnectionPae -*2' Sel Co**#a#e$ S#a#! I"&er#ers7.e enera' re4uirements for protection of t.is t"pe of eneration are co)eredit. s"nc.ronous mac.ines in cases ! to - abo)e& 8oe)er, in)erters common'"inc'ude proprietar" protection met.ods inc'udin oCo(& 7.e GeneratinCompan" s.ou'd submit detai's of protection to ascertain t.at t.e eneration isnot susceptib'e to trippin for oCo( 'ess t.an 2&- 89>s&If it is proposed t.at t.e protection rep'aces an" protection specified in t.e casesabo)e, it is t.e responsibi'it" of t.e Generatin Compan" to demonstrate t.at t.eprotection meets t.e acceptab'e 'e)e's of dependabi'it" and re'iabi'it"&


Pae --

9 SURGE PROTECTION

91 Ge"eralE4uipment associated it. an embedded enerator re4uires to be protectedfrom .a9ardous effects of transient o)er#)o'taes&Occurrence of transient o)er )o'taes can be due to e@terna' as e'' as interna'causes& Li.tnin is t.e most common source for transient o)er#)o'taes&8oe)er, damain transients cou'd oriinate from it.in t.e rid s"stem itse'f,due to sitc.in operations, ferro resonance, etc& 6de4uate measures s.ou'd be taken to protect t.e insu'ation and e4uipmentfrom bein damaed due to t.e abo)e conditions& 6n L+>8+ transformer usua''" connects t.e embedded enerator to t.e rids"stem of t.e CEB& It is essentia' t.at t.e 8+ side of t.e transformer beprotected from t.e transient o)er )o'taes b" insta''in ap'ess meta' o@ide




Pae -3

16 HAR;ONICS

8armonic )o'taes and currents produced it.in t.e Generatin Companiess"stem ma" cause e@cessi)e .armonic distortion on t.e CEB s"stem .en t.es"stems are connected&7o a)oid e@cessi)e .armonic distortion on t.e CEB s"stem, t.e EmbeddedGenerator insta''ation s.a'' be desined and operated to comp'" it. t.e criteriaspecified in Q Enineerin ecommendation G->% or BS E$ -0!/0&7estin s.ou'd be carried out it. t.e enerator connected to t.e rid andresu'ts compared to t.ose from t.e rid s"stem at t.e same point .en t.eenerator is not connected&


Pae -511 OPERATIONAL PROCEDURES AND REUIRE;ENTS

7.e operationa' re4uirements and uide'ines for an Embedded Generator fo''oin t.e commencement of commercia' operation are i)en in t.e PP6&7.e Generatin Compan" must i)e due reard to t.e re4uirements stipu'ated int.e E'ectricit" 6ct and t.e E'ectricit" eu'ations& 7.e" s.ou'd a'so ensure t.ata'' operatin personne' are competent, and t.at t.e" .a)e ade4uate kno'edeand sufficient Hudement to take t.e correct action .en dea'in it. anemerenc"&

111 ;ea"s o Isola#!o" 6'' Embedded Generators operated in para''e' it. t.e CEB s"stem must inc'udemeans of iso'ation <suitab'" 'abe''ed=, capab'e of disconnectin t.e .o'e of t.eEmbedded Generatin p'ant infeed from t.e CEB s"stem& 7.is means of

iso'ation must be 'ockab'e in t.e O(( position on'", b" a separate pad'ock& 6ccess to t.e points of iso'ation s.ou'd be kept c'ear and unobstructed&CEB s.ou'd .a)e t.e ri.ts of access to t.e means of iso'ation it.out unduede'a"& CEB .as t.e ri.t to iso'ate t.e Embedded Generators infeed at an" time,s.ou'd suc. disconnection become necessar" for safet" reasons and>or tocomp'" it. statutor" ob'iations& 7.e means of iso'ation s.ou'd norma''" beinsta''ed c'ose to t.e meterin point, but ma" be positioned e'se.ere it. prior areement it. CEB& 6 diaram s.oin a'' e'ectrica' infeeds s.ou'd be disp'a"ed at t.e Point of Supp'", or as near as practicab'e to it&

112 Ear#-!". Fa!l!#!es or ;a!"#e"a"e 6de4uate eart.in e4uipment, fi@ed or portab'e, s.a'' be pro)ided to eart. an 8+section durin maintenance& 7.ese s.a'' be pro)ided at a'' points of iso'ation of

t.e respecti)e section or beteen suc. point and t.e point<s= of ork& In t.ecase of L+ points of iso'ation of 8+ e4uipment <suc. as transformers=, if it is notpracticab'e to app'" eart.s, t.en precautions s.a'' be taken accordin to safet"ru'es&


Pae /0

12 SAFETY ASPECTS

In order to safeuard persons orkin at t.e embedded enerator insta''ationsand a'so to ensure t.e safet" of a'' its p'ant and e4uipment from t.e .a9ardoussituations, a Safet" Code s.a'' be imp'emented and used for operationa'

acti)ities& 6 Safet" Code s.a'' basica''" contain:



• esponsibi'ities of persons and t.eir definitions

• Le)e's of aut.orisation and competence

• P'ant and e4uipment t.at are in operation and t.eir definitions

• +o'tae 'e)e's

• Safet" ru'es .ic. i'' c'ear'" specif" t.e actions t.at i'' be re4uired to

safeuard t.e person>s carr"in out ork on t.e p'ant and e4uipment fromt.e in.erent daners

• 7rainin of staff to safe'" carr" out aut.orised tasks to a satisfactor"

comp'etion

• Specia'ised procedures for safet" .en ork is carried out it.out iso'ation

or eart.in

• Documentation re4uired to be comp'eted before and after a Hob is carried out

• 1anaement instructions on t.e app'ication of t.e KSafet" Code&

E)er" emp'o"ee s.a'' be issued it. a cop" of t.e Safet" Code and it is t.eresponsibi'it" of t.e embedded enerator to ensure t.at a'' ru'es and proceduresspecified in t.e Code are strict'" fo''oed&Instead of .a)in its on KSafet" Code, t.e embedded enerator .as t.e optionof adoptin t.e CEBs safet" manua' as its Safet" Code& nder suc. situations,aut.orised persons, competent persons etc& s.a'' be as defined in t.e CEBsSafet" 1anua', and .ence it s.a'' be necessar" for t.e embedded enerator toet its persona' aut.orised b" t.e CEB&7.e Safet" Code s.ou'd inc'ude t.e re'e)ant re4uirements of nationa' e'ectricit"reu'ations t.at app'" to e'ectrica' insta''ations&


Pae /!

AC@NO?LEDGE;ENTS

7.is CEB Guide for Grid Interconnection for Embedded Generators, Sri Lanka, as

de)e'oped for Ce"'on E'ectricit" Board under t.e Sri Lanka Ener" Ser)ices De'i)er"ProHect&7.e Guide as prepared b",Dr 7i'ak Si"amba'apiti"a, esource 1anaement 6ssociates <P)t= Ltd&, Sri Lanka&1r Da)id oberts, Du'as Ltd&, Q&1r 6ndre Causebrook, Econnet Ltd&, Qit. t.e assistance of,1r Ra"asiri Qarunana"ake, Sri Lanka1r 1 D R 6nt.on", Sri Lanka1r Bi'' oers, Q&7.e 7eam of Consu'tants t.ank 1r P L G Qari"aasam, ProHect Coordinator of Ce"'onE'ectricit" Board <CEB=, and a'' t.e staff of CEB for t.eir support durin studiesassociated it. t.is proHect& 7.e 7eam a'so t.anks t.e Oners and Operators of se)era' e@istin Embedded Generators, Contractors and Consu'tants, for t.eir support

it. information, discussions and p'ant )isits& Information Cop" #$ot for BiddinCEB Guide for Grid Interconnection of Embedded Generators, Sri Lanka December 2000Part 2: Protection and Operation of Grid Interconnection

Pae /2

BIBLIOGRAPHY

Ele#r!!#y A# (o Sr! La"5a) $o !5 of !5-0, $o& -- of !5--, and subse4uentamendments&G!$el!"es o" Pr!&a#e Se#or Par#!!7a#!o" !" S*all Hy$ro Po4er De&elo7*e"#, Ce"'on E'ectricit" Board, !55&S#a"$ar$!se$ A.ree*e"# or Pr-ase o E"er.y, Ce"'on E'ectricit" Board&U@ E".!"eer!". Reo**e"$a#!o" G/91< ecommendations for t.e



connection of embedded eneratin p'ant to Pub'ic E'ectricit" Supp'iersdistribution s"stems&U@ E".!"eer!". Te-"!al Re7or# No 110 (Re&!s!o" 1) (199/)< $otes of uidance for t.e protection of pri)ate eneratin sets up to - 1? for operationin para''e' it. Pub'ic E'ectricit" Supp'iers distribution s"stems&E".!"eer!". Reo**e"$a#!o" G8/ (199')< ecommendations for t.e

connection of embedded eneration p'ant, to Pub'ic E'ectricit" Supp'ierss"stems abo)e 20k+, or it. outputs o)er - 1?&U@ E".!"eer!". Reo**e"$a#!o" P2 (199)< P'annin 'imits for )o'taef'uctuations caused b" industria', commercia' and domestic e4uipment in t.enited Qindom pub'ic distribution s"stems&BS EN '1666>0>0 (199/)< Ele#ro*a."e#! Co*7a#!%!l!#y (E;C) Par# 0#Limitations of )o'tae f'uctuations and f'icker in 'o )o'tae supp'" s"stems for e4uipment it. rated current 'ess t.an !/6&E4ui)& IEC !000#%#%: !55*&BS EN '1666>0>2 (199/) A12 (a"ary 199')< E'ectromanetic Compatibi'it"<E1C= part %, Limits Section 2: Limits for .armonic current emissions<e4uipment input current N!/ 6 per p.ase=& E4ui)& IEC !000#%#2: !55-

U@ E".!"eer!". Reo**e"$a#!o" P29 (1996)< P'annin 'imits for )o'taeunba'ance in t.e nited Qindom&


Pae /%

U@ EA E".!"eer!". Reo**e"$a#!o" G/0 (198')< Limits for 8armonics int.e nited Qindom E'ectricit" Supp'" S"stem&U@ E".!"eer!". Reo**e"$a#!o" P2/< Securit" of Supp'"&Ero7ea" CENELEC S#a"$ar$ BS EN /61'6< +o'tae c.aracteristics of e'ectricit" supp'ied b" Pub'ic Distribution S"stems&

IEC2--, <BS -552= E'ectrica' e'a"s&BS *%0 <!55!= Code of Practice for Eart.in&BS /! <!552= e4uirements for E'ectrica' Insta''ationsT IEE ?irineu'ations, Si@teent. Edition&E'ectromanetic Compatibi'it"T BS E$ -003!#!: !552 <emissions= and BS E$-0032#!: !553 <immunit"=&IEC 505 <!533=T S.ort#circuit current ca'cu'ation in t.ree#p.ase 6C s"stems&U@ E".!"eer!". Reo**e"$a#!o" G83< Procedure to meet t.e re4uirementsof IEC505 for t.e ca'cu'ation of s.ort#circuit currents in t.ree#p.ase 6C poer s"stems&

Information Cop" # $ot for Biddin

grid interconnection of embedded generators not for bidding

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